The present invention relates to novel methods of cell transplantation into scar tissue in the heart in order to improve heart function, stimulate angiogenesis, and to salvage myocardium. The invention also relates to the preparation and culturing of the subject cells prior to transplantation, a mechanism for the delivery of gene therapy using such transplants, and to grafts comprising such cells.
Organ transplantation and surgical resection have been used to replace or remove diseased non-functional myocardial tissue. Recently, fetal cellular transplantation has been used to improve neurological deficiencies found in Parkinson""s disease (Tompson, L. et al., Science 257:868-870, 1992). In a similar approach, normal myoblasts have been transplanted into the skeletal muscle of patients with Duchenne muscular dystrophy (Gussoni, E. et al., Nature 356:435-438, 1992), where the transplanted cells expressed dystrophin.
Fetal ventricular cardiomyocytes, atrial tumor cells, and skeletal myoblasts have been transplanted into normal myocardium (Koh, G Y et al., Journal of Clinical Investigation 92:1548-54, 1993; Soonpaa, M H et al., Science 264:98-101, 1994; U.S. Pat. No. 5,602,301). In the studies described in these references, the cells were transplanted into the middle and thickest layer of the heart, composed of cardiac muscle, which has an excellent blood supply. Transplanted atrial tumor cells formed intercalated disc junctions with the host cardiomyocytes. Myocardial function was not assessed.
Cardiac scar tissue is formed after the ventricular wall of the heart necroses due to damage. In contrast to myocardial tissue, cardiac scar tissue contains no cardiac muscle cells. Instead, it is composed of connective tissue cells, such as fibroblasts, and non-cellular components, such as collagen and fibronectin. Cardiac scar tissue is non-contractile, and, therefore, interferes with normal cardiac function. Mature scar tissue is thought to be an inert tissue having a limited blood supply. Accordingly, the prior art suggests that cultured cells could not be successfully transplanted into mature scar tissue.
Scar tissue is much thinner than normal myocardium. In the method taught by Field in U.S. Pat. No. 5,602,301, cellular grafts are introduced into the myocardium by injection. However, this method, if applied to the much thinner scar tissue, would result in tissue ballooning and an accompanying increase in pressure within the region of cell injection. As a result, the transplanted cellular material would leak from the puncture point of the injection needle upon withdrawal, and the efficiency of such transplants would be reduced.
Thus, there is a need to develop cellular allo- and autotransplantation technology within scar tissue of the diseased myocardium to improve contractile function, minimize myocardial remodeling, stimulate angiogenesis, deliver gene therapy, rebuild the heart, and salvage damaged cardiomyocytes. The present invention addresses these needs.
It is an object of the present invention to provide cell transplantation methods for treating scar tissue in the myocardium which overcome deficiencies in the prior art. The invention illustrates that atrial myocytes, smooth muscle cells, endothelial cells, and fibroblasts can be successfully transplanted into the scar tissue formed after ventricular necrosis and into tissue membranes and porous synthetic membranes. The cell grafts form tissue that survived the three month duration of the study, improved myocardial function, limited myocardial remodeling, and stimulated angiogenesis. The presence of the grafts did not induce overt cardiac arrhythmias. When auto-cell transplantation occurred, immunorejection did not occur.
In a first aspect, the invention features a method of forming a stable myocardial graft in a mammal comprising, transplanting cells into myocardial tissue or scar tissue in the heart. Cells are chosen from the group consisting of: adult cardiomyocytes, fetal cardiomyocytes, pediatric cardiomyocytes, adult fibroblasts, fetal fibroblasts, smooth muscle cells, endothelial cells, and skeletal myoblasts.
In preferred embodiments of the first aspect of the invention, cells may be chosen from adult or fetal smooth muscle cells and fibroblasts, adult cardiomyocytes and endothelial cells may be co-transplanted, adult cardiomyocytes may be derived from atrial tissue, the graft may be derived from auto-, allo- or xenotransplantation, and the graft may comprise adult cardiomyocytes derived from autotransplantation, such as cardiomyocytes derived from atrial tissue.
In another preferred embodiment of the first aspect of the invention, the cells may be directly introduced into the myocardial tissue or the scar tissue, for example, by injection, and the injection site may be sealed with a biological adhesive to prevent leakage of the cells.
In other preferred embodiments of the first aspect of the invention the cells may be suspended on a biodegradable or non-degradable mesh, or may be transfected to deliver recombinant molecules to the myocardial tissue or the scar tissue.
In still another embodiment of the first aspect of the invention, the cells may be used in myocardial reconstructive surgery, and may be attached to the outer surface of the myocardial tissue or the scar tissue with a biological adhesive, or may be transplanted following an inflammatory response in the myocardial tissue. In addition, growth factors may be co-transplanted with the cells. Growth factors are chosen from the group consisting of: insulin-like growth factors I and II; transforming growth factor-xcex21, platelet-derived growth factor-B, basic fibroblast growth factor, and, vascular endothelial growth factor.
In yet other preferred embodiments of the first aspect of the invention, the cells are transplanted into scar tissue, and at least 10%, 20%, or 30% of the scar tissue area is occupied by transplanted cells four weeks after transplantation.
In a second aspect, the invention features a therapeutic graft for application in mammalian myocardial tissue or scar tissue in the heart, comprising transplanted cells chosen from the group consisting of: adult cardiomyocytes, pediatric cardiomyocytes, fetal cardiomyocytes, adult fibroblasts, fetal fibroblasts, adult smooth muscle cells, fetal smooth muscle cells, endothelial cells, and skeletal myoblasts.
In preferred embodiments of the second aspect of the invention, the graft may comprise adult cardiomyocytes and endothelial cells, the transplanted cells may be chosen from smooth muscle cells and fetal fibroblasts, the adult cardiomyocytes may be derived from atrial tissue, or the graft may be derived from auto-, allo- or xenotransplantation. The graft may comprise adult cardiomyocytes derived from autotransplantation and the cardiomyocytes may be derived from atrial tissue. The cells of the graft may be introduced into myocardial tissue or scar tissue by injection, and the cells may be transfected to deliver recombinant molecules to myocardial tissue or scar tissue. The graft may further comprise growth factors, for example, insulin-like growth factors I and II, transforming growth factor-xcex21, platelet-derived growth factor-B, basic fibroblast growth factor, and, vascular endothelial growth factor. Cells of the graft also may be suspended on a mesh (e.g., a biodegradable mesh).
In a third aspect, the invention features a therapeutic graft, for implantation into mammalian myocardial tissue or scar tissue in the heart, comprising a suitable biodegradable or non-biodegradable scaffolding having cells supported thereon. The cells are chosen from the group consisting of: adult cardiomyocytes, pediatric cardiomyocytes, fetal cardiomyocytes, adult fibroblasts, fetal fibroblasts, smooth muscle cells (e.g., adult smooth muscle cells or fetal smooth muscle cells), endothelial cells, and skeletal myoblasts.
In preferred embodiments of the third aspect of the invention, adult cardiomyocytes may be derived from atrial tissue, and the graft may comprise adult cardiomyocytes and adult endothelial cells. The graft may be used in cardiomyoplasty. The scaffolding of the graft may comprise Dacron or polyglycolic acid polymers with or without polylactic acid polymers, the cellular material may consist of cardiomyocytes, smooth muscle cells or endothelial cells, and the graft may further include an implantable pacemaker.
Grafts according to the third aspect of the invention may be used for closing cardiac defects, and for myocardial reconstructive surgery.
In a fourth aspect, the invention features a method of culturing cardiomyocytes from pediatric mammalian myocardial tissue comprising: a) comminuting said myocardial tissue; b) digesting said tissue for 15 minutes in a digesting solution containing 0.2% trypsin and 0.1% collagenase dissolved in phosphate buffered saline and separating the digested tissue solution from the remaining myocardial tissue; c) adding to the digested tissue solution a culture medium comprising Iscove""s modified Dulbecco""s medium (IMDM), 10% fetal bovine serum, and 0.1 mM xcex2-mercaptoethanol; culture medium being added in a ratio of 20 volumes of culture medium to 1 volume of digesting solution; d) centrifuging the resulting solution at 581xc3x97 g for 5 minutes and discarding the supernatant; e) re-suspending the pellet in fresh culture medium; f) culturing the suspension in 10% fetal bovine serum and 0.1 mM xcex2-mercaptoethanol; and, g) isolating cardiomyocytes from the culture.
In preferred embodiments of the fourth aspect of the invention the method may further include passaging cardiomyocytes by sub-culturing with a sub-culturing enzyme solution comprising 0.01% trypsin, 0.02% glucose, and 0.5 mM EDTA. The method of the fourth aspect may further include storing the cardiomyocytes by a) dissociating cultured cardiomyocytes from the culture plate using sub-culturing enzyme solution; b) adding culture medium in a ratio of 5 volumes of culture medium to 1 volume of sub-culturing enzyme solution; c) centrifuging the solution at 581xc3x97 g for 5 minutes; d) discarding the supernatant and re-suspending the pellet in 1 mL IMDM containing 20% fetal bovine serum and 20% glycerol; and, e) freezing and storing the resulting suspension in liquid nitrogen. The method may further include thawing the frozen sample at 37xc2x0 C. and culturing the cardiomyocytes for 3 to 5 days in a solution of IMDM containing 20% fetal bovine serum.
In a fifth aspect, the invention features a method of culturing cardiomyocytes from adult mammalian myocardial tissue comprising: a) comminuting said myocardial tissue; b) digesting the tissue for 15 minutes in a digesting solution containing 0.2% trypsin and 0.1% collagenase dissolved in phosphate buffered saline; c) separating the digested tissue solution and digesting the remaining tissue with fresh digesting solution for 10 minutes; d) combining both digested tissue solutions from steps (b) and (c) and adding a culture medium comprising Iscove""s modified Dulbecco""s medium (IMDM, containing 10% fetal bovine serum, and, 0.1 mM xcex2-mercaptoethanol) in a ratio of 20 volumes of culture medium to 1 volume of said digesting solution; e) centrifuging the resulting solution at 581xc3x97 g for 5 minutes and discarding the supernatant; f) re-suspending the pellet in fresh culture medium; g) culturing the suspension in 10% fetal bovine serum and 0.1 mM xcex2-mercaptoethanol; and, h) isolating cardiomyocytes from the culture.
In a preferred embodiment of the fifth aspect of the invention, the method may further include passaging the cardiomyocytes using sub-culturing enzyme solution comprising 0.01% trypsin, 0.02% glucose, and 0.5 mM EDTA.
The method of the fifth aspect also may further include storing cardiomyocytes by a) dissociating cultured cardiomyocytes from the culture plate using sub-culturing enzyme solution; b) adding culture medium in a ratio of 5 volumes of culture medium to 1 volume of sub-culturing enzyme solution; c) centrifuging the solution at 581xc3x97 g for 5 minutes; d) discarding the supernatant and re-suspending the pellet in 1 mL IMDM containing 20% fetal bovine serum and 20% glycerol; and, e) freezing and storing the resulting suspension in liquid nitrogen.
In another embodiment of the fifth aspect, the method may further include thawing the frozen sample at 37xc2x0 C. and culturing the cardiomyocytes for 3 to 5 days in a solution of IMDM containing 20% fetal bovine serum.
In a sixth aspect, the invention features a method of treating defective, damaged or scarified heart tissue, comprising transplanting into the tissue a graft of cells chosen from the group consisting of: adult cardiomyocytes, pediatric cardiomyocytes, fetal cardiomyocytes, adult fibroblasts, fetal fibroblasts, adult smooth muscle cells, fetal smooth muscle cells, endothelial cells, and skeletal myoblasts.
In preferred embodiments of the sixth aspect of the invention, the adult cardiomyocytes may be derived from atrial tissue, cells in the graft may be adult cardiomyocytes and endothelial cells, the cells may be directly introduced into heart tissue, and the graft may be a patch comprising cells suspended on a biologically acceptable biodegradable or non-biodegradable scaffolding.
In still other preferred embodiments of the sixth aspect of the invention, the cells are transplanted into scar tissue, and at least 10%, 20%, or 30% of the scar tissue is occupied by transplanted cells four weeks after transplantation.
In another preferred embodiment of the sixth aspect of the invention, the method may comprise the steps of: (a) surgically removing defective heart tissue thereby creating an opening; and, (b) attaching the graft to the opening to form a water tight seal.
In a seventh aspect, the invention features isolated cells for transplantation into myocardial scar tissue, selected from the group consisting of: adult cardiomyocytes, pediatric cardiomyocytes, adult fibroblasts, fetal fibroblasts, adult smooth muscle cells, fetal smooth muscle cells, endothelial cells, and skeletal myoblasts, wherein the cells survive in myocardial scar tissue after transplantation and improve cardiac function, relative to cardiac function of a heart having similar myocardial scar tissue that is not transplanted with cells. Cardiac function is assessed by at least one of the criteria in the group consisting of: area occupied by scar tissue; vascularization of scar tissue; blood flow to scar tissue; developed pressure, systolic pressure; end diastolic pressure; and dp/dt.
In preferred embodiments of the seventh aspect of the invention, the cells may comprise at least two of the cell types selected from the group. For example, the cells may comprise a combination of: adult cardiomyocytes and endothelial cells; pediatric cardiomyocytes and endothelial cells; or myoblasts and endothelial cells.
In an eighth aspect, the invention features a method for testing a pharmacological agent that is intended to prevent or ameliorate cardiac damage during cardiac surgery. The method comprises exposing the pharmacological agent to isolated cells selected from the group consisting of: adult cardiomyocytes, pediatric cardiomyocytes, adult fibroblasts, fetal fibroblasts, adult smooth muscle cells, fetal smooth muscle cells, endothelial cells, and skeletal myoblasts, wherein the cells survive in myocardial scar tissue after transplantation and improve cardiac function, relative to cardiac function of a heart having similar myocardial scar tissue that is not transplanted with cells (cardiac function is assessed by at least one of the criteria in the group consisting of: area occupied by scar tissue; vascularization of scar tissue; blood flow to scar tissue; developed pressure, systolic pressure; end diastolic pressure; and dp/dt), wherein cells exposed to the pharmacological agent prevent or ameliorates cardiac damage during cardiac surgery, compared to cells not exposed to the pharmacological agent.
In an ninth aspect, the invention features a method of forming a stable cardiac graft in a mammal, comprising transplanting into the scar tissue of a heart, cells chosen from the group consisting of: adult cardiomyocytes; pediatric cardiomyocytes; adult fibroblasts; fetal fibroblasts; adult smooth muscle cells; fetal smooth muscle cells; endothelial cells; and skeletal myoblasts, wherein the cells survive in scar tissue in a heart after transplantation into scar tissue, and wherein the cells improve cardiac function, relative to cardiac function of a heart having similar myocardial scar tissue that is not transplanted with such cells, wherein cardiac function is assessed by at least one of the criteria in the group consisting of: area occupied by scar tissue; vascularization of scar tissue; blood flow to scar tissue; developed pressure, systolic pressure; end diastolic pressure; and dp/dt, wherein at least 10% of scar tissue is occupied by transplanted cells four weeks after transplantation.
In other embodiments of the ninth aspect of the invention, at least 20% or at least 30% of the scar tissue may be occupied by transplanted cells four weeks after transplantation, or at least 40% or at least 50% of the scar tissue may be occupied by transplanted cells eight weeks after transplantation.
In preferred embodiments of the ninth aspect, the cells may include at least two types of cells selected from the group. For example, the cells may comprise a combination of: adult cardiomyocytes and endothelial cells; pediatric cardiomyocytes and endothelial cells; or myoblasts and endothelial cells.
In other preferred embodiments of the ninth aspect of the invention, growth factors are co-transplanted with the cells. The growth factors are chosen from the group consisting of: insulin-like growth factors I and II; transforming growth factor-xcex21; platelet-derived growth factor-B; basic fibroblast growth factor; and, vascular endothelial growth factor.
In a tenth aspect, the invention features a method of treating defective, damaged or scarified heart tissue, comprising transplanting into defective, damaged or scarified heart tissue a graft of cells, wherein the graft of cells comprises a combination of: adult cardiomyocytes and endothelial cells; pediatric cardiomyocytes and endothelial cells; or myoblasts and endothelial cells.
In preferred embodiments of the tenth aspect of the invention, the graft may be used for cardiomyoplasty, for closing cardiac defects, or for myocardial reconstructive surgery.
In an eleventh aspect, the invention features a therapeutic graft for implantation in mammalian myocardial tissue or scar tissue in a heart, comprising biodegradable or non-biodegradable scaffolding supporting cells, wherein the cells consist of a combination of: adult cardiomyocytes plus endothelial cells; pediatric cardiomyocytes plus endothelial cells; or myoblasts plus endothelial cells.
In various embodiments of the eleventh aspect of the invention, the scaffolding comprises Dacron or polyglycolic acid polymers with or without polylactic acid polymers, or further includes an implantable pacemaker.
In another embodiment of the eleventh aspect, the cells may be transfected to deliver recombinant molecules to the myocardial tissue or scar tissue.
In still another embodiment of the eleventh aspect, the graft may comprise growth factors, for example: insulin-like growth factors I and II; transforming growth factor-xcex21; platelet-derived growth factor-B; basic fibroblast growth factor: and, vascular endothelial growth factor.
In yet another embodiment of the eleventh aspect, the cells may be suspended on a biodegradable mesh.